Your question is Nextdoor-Scale Database Design. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
Design the database for the Nextdoor like system considering there is huge scale
Asked in the onsite stage. System design round.
Focus on how you would store, retrieve, and serve neighborhood posts, comments, reactions, and ranking signals at scale. Assume the product has heavy read traffic, write bursts from local events, and strict locality and privacy constraints.